In vivo expression of copper-transporting proteins in rat brain regions

Copper biodistribution after acute systemic administration of copper gluconate to rats

Neurodegenerative disorders have been linked to the decrease of copper concentrations in different regions of the brain. Therefore, intake of micronutrient supplements could be a therapeutic alternative. Since the copper distribution profile has not been elucidated yet, the aim of this study was to characterize and to analyze the concentration profile of a single administration of copper gluconate to rats by two routes of administration. Male Wistar rats were divided into three groups. The control group received vehicle (n = 5), and the experimental groups received 79.5 mg/kg of copper orally (n = 4-6) or 0.64 mg/kg of copper intravenously. (n = 3-4). Blood, striatum, midbrain and liver samples were collected at different times. Copper concentrations were assessed using atomic absorption spectrophotometry. Copper concentration in samples from the control group were considered as baseline. The highest copper concentration in plasma was observed at 1.5 h after oral administration, while copper was quickly compartmentalized within the first hour after intravenous administration. The striatum evidenced a maximum metal concentration at 0.25 h for both routes of administration, however, the midbrain did not show any change. The highest concentration of the metal was held by the liver. The use of copper salts as replacement therapy should consider its rapid and discrete accumulation into the brain and the rapid and massive distribution of the metal into the liver for both oral and intravenous routes. Development of controlled-release pharmaceutical formulations may overcome the problems that the liver accumulation may imply, particularly, for hepatic copper toxicity.

Copper Metabolism of Newborns Is Adapted to Milk Ceruloplasmin as a Nutritive Source of Copper: Overview of the Current Data

Copper, which can potentially be a highly toxic agent, is an essential nutrient due to its role as a cofactor for cuproenzymes and its participation in signaling pathways. In mammals, the liver is a central organ that controls copper turnover throughout the body, including copper absorption, distribution, and excretion. In ontogenesis, there are two types of copper metabolism, embryonic and adult, which maintain the balance of copper in each of these periods of life, respectively. In the liver cells, these types of metabolism are characterized by the specific expression patterns and activity levels of the genes encoding ceruloplasmin, which is the main extracellular ferroxidase and copper transporter, and the proteins mediating ceruloplasmin metalation. In newborns, the molecular genetic mechanisms responsible for copper homeostasis and the ontogenetic switch from embryonic to adult copper metabolism are highly adapted to milk ceruloplasmin as a dietary source of copper. In the mammary gland cells, the level of ceruloplasmin gene expression and the alternative splicing of its pre-mRNA govern the amount of ceruloplasmin in the milk, and thus, the amount of copper absorbed by a newborn is controlled. In newborns, the absorption, distribution, and accumulation of copper are adapted to milk ceruloplasmin. If newborns are not breast-fed in the early stages of postnatal development, they do not have this natural control ensuring alimentary copper balance in the body. Although there is still much to be learned about the neonatal consequences of having an imbalance of copper in the mother/newborn system, the time to pay attention to this problem has arrived because the neonatal misbalance of copper may provoke the development of copper-related disorders.

Studies of copper trafficking in a mouse model of Alzheimer's disease by positron emission tomography: comparison of 64Cu acetate and 64CuGTSM

Alzheimer's disease can involve brain copper dyshomeostasis. We aimed to determine the effect of AD-like pathology on 64Cu trafficking in mice, using positron emission tomography (PET imaging), during 24 hours after intravenous administration of ionic 64Cu (Cu(ii) acetate) and 64Cu-GTSM (GTSMH2 = glyoxalbis(thiosemicarbazone)). Copper trafficking was evaluated in 6-8-month-old and 13-15 month-old TASTPM transgenic and wild-type mice, by imaging 0-30 min and 24-25 h after intravenous administration of 64Cu tracer. Regional 64Cu distribution in brains was compared by ex vivo autoradiography to that of amyloid-β plaque. 64Cu-acetate showed uptake in, and excretion through, liver and kidneys. There was minimal uptake in other tissues by 30 minutes, and little further change after 24 h. Radioactivity within brain was focussed in and around the ventricles and was significantly greater in younger mice. 64CuGTSM was taken up in all tissues by 30 min, remaining high in brain but clearing substantially from other tissues by 24 h. Distribution in brain was not localised to specific regions. TASTPM mice showed no major changes in global or regional 64Cu brain uptake compared to wildtype after administration of 64Cu acetate (unlike 64Cu-GTSM) but efflux of 64Cu from brain by 24 h was slightly greater in 6-8 month-old TASTPM mice than in wildtype controls. Changes in copper trafficking associated with Alzheimer's-like pathology after administration of ionic 64Cu are minor compared to those observed after administration of 64Cu-GTSM. PET imaging with 64Cu could help understand changes in brain copper dynamics in AD and underpin new clinical diagnostic imaging methods.

Ceruloplasmin gene expression profile changes in the rat mammary gland during pregnancy, lactation and involution

Copper metabolism disturbances in mammary gland (MG) cells have severe consequences in newborns. The mechanism that controls the balance of copper in the MG has not been thoroughly characterized. Four primary copper homeostasis genes in mammals: (1) ceruloplasmin (Cp) encoding multifunction multicopper blue (ferr)oxidase; (2) CTR1 encoding high affinity copper importer 1; and (3 and 4) two similar genes encoding Cu(I)/Cu(II)-ATPases P1 type (ATP7A and ATP7B) responsible for copper efflux from the cells and metallation of cuproenzymes formed in the Golgi complex are expressed in MG. This study aimed to characterize expression of these genes during pregnancy, lactation and forced involution in the rat MG. We found that Cp anchored to the plasma membrane and ATP7A were expressed during pregnancy and lactation. Soluble Cp and ATP7B were highly expressed in lactating MG decreasing to its ending. CTR1 activity increased during MG growth and reached its maximum at postpartum and then it decreased until the end of lactation. During early forced MG involution, Cp gene expression persisted; while a form of Cp that lacked exon 18 appeared. We suggest that Cp gene expressional changes at the transcriptional and posttranscriptional level reflect various physiological functions of Cp proteins during MG remodeling.

Systems biology approach to Wilson's disease

Wilson's disease (WD) is a severe disorder of copper misbalance, which manifests with a wide spectrum of liver pathology and/or neurologic and psychiatric symptoms. WD is caused by mutations in a gene encoding a copper-transporting ATPase ATP7B and is accompanied by accumulation of copper in tissues, especially in the liver. Copper-chelation therapy is available for treatment of WD symptoms and is often successful, however, significant challenges remain with respect to timely diagnostics and treatment of the disease. The lack of genotype-phenotype correlation remains unexplained, the causes of fulminant liver failure are not known, and the treatment of neurologic symptoms is only partially successful, underscoring the need for better understanding of WD mechanisms and factors that influence disease manifestations. Recent gene and protein profiling studies in animal models of WD began to uncover cellular processes that are primarily affected by copper accumulation in the liver. The results of such studies, summarized in this review, revealed new molecular players and pathways (cell cycle and cholesterol metabolism, mRNA splicing and nuclear receptor signaling) linked to copper misbalance. A systems biology approach promises to generate a comprehensive view of WD onset and progression, thus helping with a more fine-tune treatment and monitoring of the disorder.

Differential expression of ATP7A, ATP7B and CTR1 in adult rat dorsal root ganglion tissue

BACKGROUND

ATP7A, ATP7B and CTR1 are metal transporting proteins that control the cellular disposition of copper and platinum drugs, but their expression in dorsal root ganglion (DRG) tissue and their role in platinum-induced neurotoxicity are unknown. To investigate the DRG expression of ATP7A, ATP7B and CTR1, lumbar DRG and reference tissues were collected for real time quantitative PCR, RT-PCR, immunohistochemistry and Western blot analysis from healthy control adult rats or from animals treated with intraperitoneal oxaliplatin (1.85 mg/kg) or drug vehicle twice weekly for 8 weeks.

RESULTS

In DRG tissue from healthy control animals, ATP7A mRNA was clearly detectable at levels similar to those found in the brain and spinal cord, and intense ATP7A immunoreactivity was localised to the cytoplasm of cell bodies of smaller DRG neurons without staining of satellite cells, nerve fibres or co-localisation with phosphorylated heavy neurofilament subunit (pNF-H). High levels of CTR1 mRNA were detected in all tissues from healthy control animals, and strong CTR1 immunoreactivity was associated with plasma membranes and vesicular cytoplasmic structures of the cell bodies of larger-sized DRG neurons without co-localization with ATP7A. DRG neurons with strong expression of ATP7A or CTR1 had distinct cell body size profiles with minimal overlap between them. Oxaliplatin treatment did not alter the size profile of strongly ATP7A-immunoreactive neurons but significantly reduced the size profile of strongly CTR1-immunoreactive neurons. ATP7B mRNA was barely detectable, and no specific immunoreactivity for ATP7B was found, in DRG tissue from healthy control animals.

CONCLUSIONS

In conclusion, adult rat DRG tissue exhibits a specific pattern of expression of copper transporters with distinct subsets of peripheral sensory neurons intensely expressing either ATP7A or CTR1, but not both or ATP7B. The neuron subtype-specific and largely non-overlapping distribution of ATP7A and CTR1 within rat DRG tissue may be required to support the potentially differing cuproenzyme requirements of distinct subsets of sensory neurons, and could influence the transport and neurotoxicity of oxaliplatin.